yes you can use rekordbox
then you gotta find your tracks (musics) and put them into rekordbox, another option (not free) you can also subscribe to a plan with TIDAL or Soundcloud to directly use It in rekordbox

You need special software, usually rekordbox is used, where you can upload your tracks. Otherwise there are countless videos on youtube on this topic.

I use beatport and tidal. Remember, with mp3 the quality of the recording is important. But you can use your own MP3 as described by Ayala